Discordant utility of ideal body weight and body mass index as predictors of mortality in lung transplant recipients

Background: An upper limit of 130% predicted ideal body weight (PIBW) has been promulgated for assessing lung transplant (LTx) candidacy, but no data in the lung transplant population support this value. A prior study used body mass index (BMI) to suggest greater mortality risk in obese allograft recipients, but the number of studied patients was small. Methods: Pre-operative PIBW percentage and BMI were obtained for all first-time, adult LTx recipients at our institution (n = 283). We compared survival data at 90 days and as of July 31, 2002, using multivariable regression and Cox modeling. Results: There were 46 obese (BMI ≥ 30) patients and 72 patients >130% PIBW, including 43 patients previously thought to fall within a normal PIBW range who were reclassified as overweight for this analysis. Cox modeling revealed no significant impact of PIBW (>130% or continuous) or BMI (>30 kg/m ² or continuous) on overall survival. Predicted ideal body weight also had no influence on 90-day mortality. When we tested PIBW in the group previously deemed of acceptable weight, we likewise found no association with mortality at 90 days or overall. For BMI only, 90-day odds ratios for death were significantly greater for obese (BMI ≥ 30; odds ratio, 3.16; 95% confidence interval, 1.05-9.48) patients than for normal-weight patients. Conclusion: Indices of pre-operative obesity did not predict long-term outcome in this large cohort of LTx recipients. The data suggest that BMI stratification may identify a group of patients at risk for increased short-term mortality, whereas PIBW is not a significant outcome predictor.